1. Field of the Invention
The present invention relates to a method and apparatus for automatically piecing slivers in a spinning process using a roving frame or a drawing frame.
2. Description of the Related Arts
In general, a sliver piecing operation is carried out by hand, i.e., one sliver end is overlapped with another sliver end by a length measured by eye, and the overlapped ends are pressed between the palms and rubbed together. This manual operation, however, requires considerable skill, and even an expert cannot always ensure that the pieced portion of the slivers has a sufficient mechanical strength and a uniform thickness, and thus the pieced portion is often broken or irregularly drafted in the subsequent spinning process, to thereby deteriorate the quality of the resultant yarn.
To solve the above problems, an apparatus for mechanically piecing sliver ends is proposed in Japanese Examined Patent Publication No. 38-5867. In this apparatus, each of the old and the fresh slivers to be pieced is nipped by two pairs of rollers spaced from each other by a predetermined length, one pair of rollers is moved away from the other so that the nipped sliver is severed and a tapered end with fiber tuft is obtained, and a trailing portion of the old sliver and a leading portion of the fresh sliver are overlapped with each other so that one fiber tuft is complemented by the other fiber tuft to thereby form a proper sliver thickness. Then the overlapped portion is pierced by needles, which then are moved laterally to widen the width thereof, and after the needless are removed, the overlapped fiber tufts are rubbed together, to be intermingled with each other by the axial reciprocation of top and bottom rollers of a group of nip rolls, in opposite directions.
In the prior art sliver piecing, a length of the fiber tuft forming the sliver end to be overlapped is defined by a mean staple length, due to the formation thereof, and is limited to at most twice a mean staple length. Also, since needles are used for enhancing the entanglement of fibers in the overlapped portion and widening the width thereof, the fibers are liable to be bent and the parallelism thereof lost. Under such circumstances, even though the top and bottom rollers of the nip rolls are reciprocated in opposite directions to each other, while nipping the overlapped portion therebetween, the fibers in the overlapped portion cannot be sufficiently entangled so that the overlapped portion is given a mechanical strength that can withstand the following spinning processes.